The known in the art Rubik's Cube™ puzzle consists of 26 cubic elements and interior central connecting mechanism. As disclosed by Rubik in HU 170,062 and later by Sugden in U.S. Pat. No. 6,974,130 cubic elements are connected to neighbor elements or to central mechanism by cam connectors of specific shapes. Those connectors are attached to unexposed part of cubic elements. Assembled puzzle has six flat exposed outer surfaces each formed by nine surfaces of cubic elements, which are used to formulate the puzzle problem to be solved, e.g. they can carry colors, patterns, figures, symbols, signs or else. All cubic elements are connected so that any of nine elements, belonging to the same outer surface of the cube can be rotated about the axis going through the center of that surface and puzzle geometrical center. The object of the game is to restore the initial undisturbed state of the cube from its disturbed state by means of rotation of groups of nine elements.
Since classic 3×3×3 cube is difficult to solve for many children there were efforts in the art to change the level of difficulty. Rubik's Cube™ puzzle level of difficulty depends on number of combinations defined by total number of elements, and can be reduced as disclosed by Rubik in U.S. Pat. No. 4,378,116 for 2×3×3 cube and U.S. Pat. No. 4,378,117 for 2×2×2 cube or can be increased as disclosed by Sebesteny in U.S. Pat. No. 4,421,311 for 4×4×4 cube or by Krell in U.S. Pat. No. 4,600,199 for 5×5×5 cube. The assembly difficulty can also be reduced by increasing the number of possible solutions by means of using less colors, e.g. two- or three-color cube or cube with two-color patterns disclosed by Sugden in U.S. Pat. No. 6,974,130. In this case not all elements will have their unique position. Although reducing number of colors without changing element shape can significantly simplify Rubik's puzzle and can lead to loss of motivation. Thus there is a need for a puzzle with a motivating balance between number of elements, their colors and shapes.
Imagination skills required to solve Rubik's cube puzzle of all sizes and its spherical or other geometrical and stereo metrical modifications are based on outer surface color or pattern perturbation, which might be not suitable for those children or adults, who prefer spatial relationships to color ones, or for color-blind or blind people. Thus there is a need for element shape variation to develop players' different imagination skills.
There are 3-D puzzles known in the art referenced in the present invention that use not only colors but also shapes of rotatable elements. Amusement device disclosed by Ayers in U.S. Pat. Nos. 4,708,345 and 4,881,738 used cylindrical shape of elements forming a regular polygon and rotatable about their longitudinal axis and divided into halves rotatable about axis orthogonal to polygon plane to assemble the puzzle. Those puzzles use outer surfaces as a key for puzzle problem formulation and/or solution but they do not use puzzle interior space. Thus there is a need for using of puzzle internal 3-D space to make it more entertaining and challenging and with variable level of difficulty.